The invention relates to a fixed roll apparatus of a fixed roll machine for crankshafts which is of scissors construction and wherein two pivotable scissors arms disposed opposite one another bear a fixed roll head and a support roll head respectively, the support roll head having two axis-parallel support rolls whose axes lie in a common plane with a drive device which generates the closure and opening movement of the fixed roll apparatus and also generates the fixed roll force.
Fixed roll apparatuses of the kind specified are known from German Patent Specification DE 197 22 308 C1, which discloses a fixed roll machine for crankshafts.
In such a fixed roll machine a fixed roll apparatus can be associated with each main bearing pin and connecting rod bearing pin of a crankshaft.
The construction of the fixed roll machine is such that during the closure of each fixed roll apparatus, first the support rolls of the support roll head and then the fixed rolls of the fixed roll head are forced against a main bearing pin or a connecting rod bearing pin, the support roll head and the fixed roll head each performing a pivoting movement in succession.
The pivoting movement of the support roll and fixed roll heads in the closure direction involves the risk that the support roll and fixed roll heads may collide with the crankshaft in the zone of an oil collar, since there is only a small free space between the support roll and fixed roll heads on the one hand and the two oil collars of a main bearing pin or a connecting rod bearing pin on the other.
It is an object of the invention so to construct a fixed roll apparatus of the kind specified that the pivoting movement of the support roll and fixed roll heads in the closure direction cannot cause any collision with the crankshaft in the zone of an oil collar.
This problem is solved according to the invention by the features that the support roll head has at least one axial guide roll which is disposed in front of the support rolls in the pivoting direction for the closure of the scissors arm bearing the support rolls, whose axis of rotation is perpendicular to the axis of rotation of the crankshaft and lies in a plane which encloses an acute angle with the plane of the axes of rotation of the support rolls, and whose diameter is larger than the width of the support roll head and slightly smaller than the spacing of the oil collars of a main bearing pin or a connecting rod bearing pin.
The invention ensures that if during the closure operation of the fixed roll apparatus the guide roll knocks against an oil collar, the fixed roll apparatus is straightened in the axial direction of the crankshaft.
Such an alignment of the fixed roll apparatus ensures that even during the pivoting movement of the fixed roller head in the closure direction no collision can take place between the fixed roll head and the crankshaft in the zone of an oil collar.
In case the acute angle between the plane containing the axis of rotation of the axial guide roll and the common plane formed by the axes of rotation of the two support rolls falls to zero, the axial guide roll has a spacing from said common plane. The external contour of the axial guide roll can also have not only the conventional cylindrical shape, but other shapes being, for example, crowned or made up of a number of geometrical shapes.
For processing particularly wide shaft bearing pins it is possible to use not only one but several axial guide rollers which are disposed one beside the other and fill the free space circumscribed by two adjacent oil collars. Usually these are two axial guide rolls whose external width is such that the two axial guide rolls fit into the free space between the oil collars with a small lateral clearance. Such an arrangement also has the advantage that the axial guide rolls are relatively small. As a result, at the same time the lateral friction between the axial guide rollers and the oil collars is reduced.